(i) Field of the Invention
This invention relates to physiologically-active novel peptides, more specifically, physiologically-active peptides having smooth muscle relaxing action, diuresis, natriuresis, vasodilation action, antihypertensive action and the like, as well as salts thereof.
(ii) Description of the Related Art
Owing to the advancement in purification and analytical equipment such as high-performance liquid chromatography, amino acid analysis and vapor-phase sequencer, peptides which exhibit interesting physiological activities in a trace amount have been discovered one after another in recent years, thereby making it clearer that a peptide takes an important role as a neurotransmitter or endocrine hormone in living bodies. For example, isolation and identification have been carried out on peptides showing an action similar to conventional amine-based neurotransmitters, such as substance P, neurotensin, vasoactive intestinal polypeptide, neuromesine K and neuromesine L; hormone-like peptides which exist in the hypothalamus and control the secretion of pituitary hormones, such as LH-RH, thyrotrophin releasing hormone (TRH) and growth hormone releasing hormone (GRH); peptides of endogenous nerve factors having opiate activity, such as enkephalin and endorphin; peptides resembling endocrine hormones, such as insulin, calcitonin and atrial natriuretic polypeptide; etc. The investigation of peptides has now been carried on in the molecular level.
In addition, the application of these peptides as therapeutics and diagnostics has also been investigated, resulting in the utilization of some of the peptides as medicines.